Diesel generator wire grounding and UPS matching instructions
With the development of industry, diesel generator sets are widely used. Due to the working characteristics of diesel generator sets, their safety requirements are becoming higher and higher. The grounding function of diesel generator sets is an important part to ensure their safety performance. In some industries, problems with electricity are not allowed. Some factories are used with UPS to prevent accidents. The following is a brief introduction to the grounding of diesel generator sets and UPS matching instructions.
Three types of grounding for diesel generators
Working grounding is to ground the neutral point, its purpose is:
1) Reduce the electric shock voltage. For a diesel generator set that is not grounded at the neutral point, when one phase is grounded and the human body touches one of the other two phases, the shock voltage is more than 1.7 times the phase voltage; while for a neutral grounded system, the shock voltage drops to close to Or equal to the phase voltage.
2) Quickly cut off the faulty equipment. For a system that is not grounded at the neutral point, when one phase is grounded, the current path can be formed due to the presence of capacitance and insulation resistance in the wire and the ground. The grounding current is very small, which is not enough to cause the protective device to operate and cut off the power. It cannot ensure personal safety. . For a system grounded at a neutral point, when one phase is grounded, the grounding current is large, and the protection device will quickly operate to disconnect the fault point.
3) Reduce the insulation level of electrical equipment to ground. In a system where the neutral point is not grounded, when one phase is grounded, the voltage of the other two phases to ground will be increased to the line voltage. For a system grounded at a neutral point, when one phase is grounded, the voltage to ground of the other two phases is only close to the phase voltage, so the insulation level of electrical equipment and transmission lines can be reduced.
2. Protective ground
The protective grounding of diesel generator sets is often used in low-voltage systems where the neutral point is not grounded. Its role is: when the insulation structure of a certain winding of the motor has been damaged and the casing is charged, if it is not grounded, the human body touches the casing, which is equivalent to a single-phase electric shock. There is a danger of electric shock. If a protective ground is used, when the human body touches the shell, the human body resistance is parallel to the ground resistance, and because the human body resistance is much larger than the ground resistance, the current passing through the human body is very small, and there is no danger of electric shock.
The protective zero connection is often used in low-voltage systems with a neutral point grounded. Its role is: when the insulation structure of a certain winding of the motor is damaged and connected to the housing, a single-phase short circuit is formed due to the use of the protective zero connection. The fuse in this phase is blown and the case is no longer charged. Even when the human body touches the case before the fuse is blown, because the human body resistance is much larger than the line resistance, the current through the human body is very small, and there is no danger of electric shock.
Matching method of generator set and UPS equipment
To improve the matching problem between the standby generator set and the UPS equipment, while trying to select a diesel generator set with excellent performance, attention should be focused on improving the input characteristics of the UPS and improving the connection between the two.
According to UPS capacity, the capacity ratio of a traditional double-conversion on-line UPS supporting generator set is generally 2 to 4 times. In fact, Tears generally works at 50% to 80% of the rated capacity, and for a generator set, its output power may be about 30% of the rated capacity.
In this way, not only the capacity of the generator set cannot be fully utilized, the equipment investment is increased, and the phenomenon of "large horse-drawn carts" is caused. In addition, the generator set is more fault-tolerant, the maintenance amount is increased, and the working reliability of the generator set is reduced.
The reason is that according to the characteristics of diesel generators, if the engine is operated under low load for a long period of time, the temperature in the cylinder is low, the lubricating oil normally entering the cylinder cannot be completely burned, and the fuel cannot be fully burned, resulting in piston ring, fuel injection The carbon deposits at the mouth are serious, and the abrasion of the cylinder is aggravated, so the failure of the above parts is accelerated, the working performance of the diesel diesel generator system is reduced, and the exhaust gas emits black smoke.
The above-mentioned instructions on the grounding of the diesel generator set and UPS matching are briefly introduced. I hope this knowledge will be helpful to you!
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